1. Field of the Invention
The present invention relates to an information exchange system for exchanging information between a road-side communication unit and a vehicle-mounted communication unit in a traffic information system.
2. Description of the Related Art
As an information exchanging technology for exchanging information between a radio communication equipment mounted on a traveling vehicle and a radio communication equipment having narrow communication region on the road, which later radio communication equipment is installed on the road-side, there have been methods to realize bidirectional communication between the road-side radio communication equipment which will be occasionally referred to as "road-side unit", and the vehicle-mounted radio communication equipment which will by occasionally referred to as "vehicle-mounted unit", by providing a vehicle detector disclosed in Japanese Unexamined Patent Publication No. Heisei 6-96387, optical receiver for a high speed data transmission disclosed in Japanese Unexamined Patent Publication No. Heisei 6-276157, TDMA network protocol structure for reader-transponder communication disclosed in Japanese Unexamined Patent Publication No. Heisei 6-61937.
In Japan, it has been started an information service
In Japan, it has been started an information service called VICS (Vehicle Information and Communication System) for mainly transmitting a traffic related information from the road-side unit to the vehicle-mounted unit. In VICS, a narrow region radio communication, a radio wave beacon system and an optical beacon system are employed and a wide region radio communication, an FM multiplex system is employed.
As a vehicle-mounted unit adapted for VICS, various types of equipment, such as a VICS receiver unit disclosed in Japanese Unexamined Patent Publication No. Heisei 9-133535, for example, have been put into practice. Regularly updated traffic related information, such as traffic-jam information, travel information, accident information, construction information and so forth, is transmitted to the vehicle. Amongst, the optical beacon system utilizes the vehicle detector disclosed in Japanese Unexamined Patent Publication No. Heisei 6-96387 and includes information communication function from the vehicle-mounted unit to the road-side unit. Currently, studies have been in progress to transmit destination information and travel time information of the vehicle from the vehicle-mounted unit to the road-side unit.
By using a narrow region road-vehicle communication, such as the VICS, the traffic related information can be transmitted to the vehicle. However, in the currently available service, the information to be transmitted to the vehicle is limited to the traffic related information. It has been considered that a system for improving convenience of a vehicular driver by transmitting a service information of service providers along the traveling road, such as restaurant, gasoline station, shop, in addition to or in place of the traffic related information.
However, in the narrow region road-vehicle communication, since a period, in which the vehicle passes the communication region, is limited, an amount of information to be transmitted to the vehicle is limited. Therefore, it becomes necessary to certain selection of service information to be provided in order to establish a system which can provide practically useful service information.
In the conventional system providing the traffic related information, in consideration of a certain range around the beacon, traffic information relating to roads within that range is picked up and transmitted to the vehicle. A selection range is varied depending upon kind of the road in such a manner that traffic information of greater distance for the road of greater importance. As set forth above, a viewpoint from the road is dominant for the traffic information. Therefore, the information to be provided is uniform for all of vehicles mounting the radio communication units.
On the other hand, concerning the information of the service providers along the road, amount of information becomes greater for providing information of content of services more accurately. On the other hand, while the traffic information is the information commonly required for all drivers of the vehicles, content of service information to be desired or required for each individual driver is different. Therefore, if manner of selection of information as being conventionally taken in the traffic information is used as is, it is possible that the information desired or required by the driver cannot be provided appropriately.